1. Field of the Invention
The invention relates to a method for the manufacture of a magnesia-carbon brick, comprising the steps of:
a. preparing a mixture comprising: PA1 b. pressing a brick from the mixture. PA1 1 the preparation of the mixture takes place at an elevated temperature in the temperature range of 30.degree. to 100.degree. C., and PA1 2 there is used a binder solution in which the percentage by weight of the solvent relative to the weight of novolak resin and solvent together is in the range 5 to 30%.
1. burned magnesite PA2 2. carbon PA2 3. a binder solution comprising: PA2 4. a hardener for the resin.
3.1 pre-condensed novolak resin PA3 3.2 a solvent for this novolak resin.
The invention also provides bricks produced by the method and a converter having a wear lining consisting at least partly of such bricks.
2. Description of the Prior Art
By a magnesia-carbon brick there is understood a brick based mainly on the components burned magnesite, carbon in the amount of typically 5-30% carbon by weight and a suitable binder. Magnesia-carbon bricks are used in the wear lining of a converter for steel production, and are substantially more resistant to wear than magnesite bricks in which the percentage of carbon used is not so high. The wear lining of a converter can, depending on the price of the bricks, be wholly or partly constructed from magnesia-carbon bricks, especially at the location of the trunnions of the converter, where the wear is greatest.
The invention should be considered against the background of the state of the art, in which it is not possible for an expert to predict either the problems arising in the preparation of bricks or the properties of a brick in dependence on the factors influencing it.
A method of the type described above is disclosed in U.S. Pat. No. 4,248,638. In this known method, the percentage by weight of solvent relative to the weight of novolak resin and solvent together is in the range 20 to 60%. According to the disclosure, with less than 20% solvent it is impossible to prepare the mixture, because the viscosity of the binder solution is more than 400 poise at 25.degree. C.
A problem of this known method is that cracks appear in the bricks after the pressing of the bricks. This is attributed by the present applicant to the presence of much air in the mixture after the mixing of the components for magnesia-carbon bricks, which air is trapped in the bricks during pressing of the bricks and compressed, so that after the bricks are pressed the expansion of the trapped air results in cracking.